Technical Field
The present disclosure relates to a terminal with a reduced possibility of cracking during crimping and springback after crimping as well as an improved anticorrosion property, a method of manufacturing thereof, and a termination connection structure of an electric wire.
Background Art
In the related art, a connection between an electric wire and a terminal in an automotive wire harness or the like is generally a crimp connection in which an electric wire is crimped with a terminal which is referred to an open barrel type. However, with an open barrel type terminal, when moisture or the like comes into contact with a connecting part (contact point) between the electric wire and the terminal, oxidation of a metal surface of the electric wire and/or the terminal progresses, and an electric resistance at a connecting part will increase. When metals used for the electric wire and the terminal are different from each other, galvanic corrosion progresses. Progression of metal oxidation and corrosion at the connecting part causes a crack and a poor contact at the connecting part, and an influence on a product life cannot be avoided. Particularly, in recent years, wire harnesses having an electric wire made of an aluminum alloy and a terminal base material made of a copper alloy are put to practical use, and thus problems of oxidation and corrosion of the connection part are becoming more prominent.
In order to prevent corrosion of an aluminum wire at the connecting part, Japanese Laid-Open Patent Publication No. 2004-199934 discloses that the terminal is made of an aluminum alloy of the same material type as that of a wire conductor to suppress galvanic corrosion which occurs in the case of a copper terminal of the related art. However, in a case where an aluminum alloy is used for the terminal, strength and spring characteristics of the terminal per se are not sufficient. Further, in order to compensate for the above, a structure incorporating a spring made of an iron-based material in the terminal is employed, and thus there is a problem of galvanic corrosion between a spring member and a terminal base material (aluminum) and a problem of an increased production cost due to time and efforts required for assembling.
Japanese Patent No. 4598039 discloses a configuration in which, in order to protect a connection part between the electric wire and the terminal, a copper cap is attached to a portion of an aluminum wire where a conductor is exposed. However, there is a problem of an increased volume of a crimp portion due to an existence of the cap and a problem of a bad crimp connection and an increased production cost due to an increase in number of parts.
Further, in Japanese Laid-Open Patent Publication No. 2011-222243, a method of molding an entire crimp connection portion with a resin is employed, and there is a problem of an increased size of a connector housing due to an enlarged mold portion, which makes it difficult to make the entire wire harness with a high-density and miniaturized structure, and a problem that a process of manufacturing a wire harness and an operation thereof become more complicated. Japanese Laid-Open Patent Publication No. 2004-207172 discloses employing a method in which, in order to shield an aluminum conductor from outside, a metal cap is provided to cover the wire conductor and thereafter a crimp piece of the terminal is further crimped. However, there is a problem that a process of attaching the aforementioned metal cap to each conductor before crimping the crimp piece of the terminal metal fitting is cumbersome and a problem of an immersion due to breakage of the metal cap by a wire barrel during crimping.
In view of such a situation, how to avoid oxidization or corrosion of a connecting part between an electric wire and a terminal base material and to prevent cracking during crimping and springback after crimping is problematic. Further, how to maintain strength of a connecting part between the electric wire and the terminal and to increase durability and reliability thereof, while preventing the connecting part from having an increased size as well as preventing a complicated connecting process and an increased cost, is problematic. Herein, “springback” is a phenomenon in which a deformed portion tends to return to its original shape. As for the terminal, it is a phenomenon in which a deformed portion of a tubular crimp portion that is crimp connected with the electric wire tends to return to its original shape by an elastic force or the like. When springback occurs in the crimp portion of the terminal, a gap is produced between an inner surface of the tubular crimp portion and the electric wire. This not only causes a contact failure between the electric wire and the terminal but also allows intrusion of moisture into the gap, and may cause corrosion.